Milk

How milk is made

From the cow to the carton is a high-tech process. Dairy farming used to be hard labour as cows were all milked by hand. These days, technology streamlines the process to make it very efficient. Suction cups are secured to the cows’ teats.

The milk goes through a series of stainless steel pipes to large refrigerated vats and is stored at 4°C. Within 48 hours, sterile refrigerated tankers take it to the milk factory, where it's pasteurised and homogenised at the same time.

Pasteurisation

This is the name given to the process whereby milk is partially sterilised resulting in extended shelf life. Milk is heated to 72°C for no less than 15 seconds and cooled immediately, destroying any harmful bacteria and micro-organisms.

Homogenisation

In the days of milk bottles and aluminium tops, cream would separate and rise to the top of the bottle. Homogenisation passes the milk under pressure through very fine nozzles, evenly dispersing the fat globules to create a smooth, creamy texture and taste.

The milk is now all set to be transformed into a wide range of dairy products, including cream, yogurt, cheese, ice cream, butter, or other types of milk such as skim, powdered, condensed, evaporated or flavoured milk.

Milk Standardisation

The taste of milk generally depends on the levels of fat and protein in particular products.

Because milk is a natural food that comes straight from the cow, its composition can vary weekly or monthly due to what phase of the lactation cycle the cow is in, what the cow is fed, its breed and what farm it’s from. Regional and seasonal factors also contribute to differences in milk composition.

Processors review the composition of milk when it is delivered to them and standardise the components in milk to ensure consumers know they will receive the same consistent, quality product every time they purchase milk, and to ensure every component of milk is used efficiently to maximise the yield and prevent waste.

Today’s farm technology, cattle management and factory methods enable greater control and therefore give more consistency in milk production. Cows on irrigated pastures will produce milk with the most consistent composition. Milk composition can be adjusted using today’s technology.

Special varieties of milk require adjustment to either reduce fat levels or increase nutrient content. The following methods also assist in standardising the milk composition for year-round consistency, although regional differences may still occur.

Centrifugal Separation

Removes some or all of the cream to produce reduced-fat, low-fat or skim milk. Skim milk solids may then be added to retain taste and increase the level of important nutrients such as protein and calcium. These additions make the flavour and mouthfeel of the milk more appealing.

Ultrafiltration

Pumps milk across a membrane under moderate pressure. This process holds back the protein and fat globules, together with a high proportion of the valuable calcium complexes, while allowing some of the water and lactose to pass through. The result is a product rich in protein and calcium with a fat content adjusted to suit the consumer.

Reverse Osmosis

A similar process to ultra-filtration, however the membrane holds back nearly all milk solids and only allows water to pass through. Note that lactose is retained in this process. There is no impact on flavour.

Ultra Osmosis

A hybrid of the previous two processes, it holds back milk solids but allows water and salt to pass through.

Spray Drying

Removes the remaining water from milk to create powdered milk products. The high nutritional value of the milk product is unimpaired.

Permeate:everything you need to know

Most dairy manufacturers standardise the fat and some may standardise protein levels of the milk collected to meet consumer expectations for a consistent product all year-round.

One process some manufacturers use to produce a variety of dairy products is ultra-filtration. In this process milk is put through a very fine filter to separate the lactose, minerals and vitamins from the water and protein. The milk-sugar (lactose), vitamins and minerals that filter through are given the term ‘permeate’ and are a valuable part of fresh milk.

Permeate is a technical term which applies to all membrane filtration processes used across food production and other industries. For example, when producing apple juice the fruit is put through a similar filtration process where permeate is the clear juice we end up buying and consuming.

The ultra-filtration process is one way to standardise the protein to a constant value throughout the year. Some other ways include adding or removing fat. Government regulations ensure that milk products conform to food standards for quality, consistency and food safety.

The composition of milk is governed by the Food Standards Australia New Zealand Food Standards Code. These standards are consistent with international standards – milk consumed in nearly all developed countries will have very similar standards. The Code allows manufacturers to add or withdraw milk components to standardise the composition of milk sourced from dairy farms, as required, to produce nutritionally consistent and safe products. Under the Code, the standard for packaged full-fat milk requires that it contain at least 3.2% of fat and 3.0% of protein.

By and large, consumers want to know that every time they purchase fresh milk it will have a consistent composition and taste and standardising milk gives consumers this consistency.

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